A histogram is a chart that shows frequencies for equal width intervals of values of a metric variable. A company wants to know how monthly salaries are distributed over 1,110 employees having operational, middle or higher management level jobs. The screenshot below shows what their raw data look like.
The snowflake schema is a variation of the star schema, featuring normalization of dimension tables. In computing, a snowflake schema is a logical arrangement of tables in a multidimensional database such that the entity relationship diagram resembles a snowflake shape. The snowflake schema is represented by centralized fact tables which are connected to multiple dimensions..
The normalization splits up the data into additional tables. Unlike Star schema, the dimensions table in a snowflake schema are normalized. For example, the item dimension table in star schema is normalized and split into two dimension tables, namely item and supplier table. Now the item dimension table contains the attributes item_key, item_name, type, brand, and supplier-key. The supplier key is linked to the supplier dimension table.